Frozen fish is usually caught, cleaned and deep frozen on board factory ships and brought ashore in an international standard 16.5 pound block or slab which measures 19.times.10.times.2.5 inches. The standard block is delivered at a temperature of -5.degree. to +5.degree. F. to a fish processing plant where it is subjected to a series of cutting steps to produce fish sticks or other portions of suitable size and shape for the retail and food service markets. All of the commonly available stick and portion sizes are direct derivatives of the above block dimensions and are usually produced in three cutting steps. The steps are commonly referred to in the industry as logging, slabbing and portioning, which terms describe the shape and size of the product resulting from each step. In the case of a block that is divided into fish sticks, the resulting pieces are usually about 3-4 inches long and 1/2-3/4 inch in rectangular cross section.
There are three common techniques used in the industry to make these cuts. In the most common technique, the fish blocks are advanced by a conveyor into a band saw or multiple-band band saw which divides the block into a plurality of portions. This procedure allows for production flexibility, but, it creates a considerable yield loss in the form of sawdust. Another common technique is to advance the blocks past a rotary saw blade in a machine similar to a table saw. Here again, sawdust losses can be substantial.
There have also been developed cutting apparatus which utilize driven rotary knife blades, in lieu of saw blades, which are able to slice through the frozen fish blocks in such a way as to minimize product wastage. Examples of such apparatus are disclosed in U.S. Pat. Nos. 2,941,560 and 4,934,237. However such cutting machines whose cutting blades rotate at relatively high speed invariably require that the blades be relatively thick in order to have the lateral stability necessary to withstand the opposing forces that are developed during the cutting process. Thus the blades produce a relatively wide cutting swath through the block which can cause chipping of the product material at the cut. Also, the blades tend to be relatively expensive particularly when the blades are provided with a specially formed cutting edge or a diamond-tipped cutting edge as described in the latter patent above.
We are also aware that some high volume producers use a slicing technique which does not create any sawdust, but which requires that the fish blocks be warmed to 20.degree. F. or more prior to cutting. This tempering step is accomplished by loading the blocks into a holding room and subjecting them to microwave energy which adds significantly to the processing cost.
Thus, until now, producers have been unable to effectively and economically divide deep-frozen fish blocks because of the hardness of the blocks.